I’ve been spending this semester experimenting in casting
techniques. Tonight I delved into Sand Casting using Pro-Craft
CASTING SAND. All went well, however I was surprised at the Sand
(or the binder really) catching on fire. After breaking out I
threw away the burned parts but retained the unburned portion to
reuse. That remainder seemed ok and quite workable, is it? Is
the blackened portion good for anything? By the way I was casting
"Jeweler’s Bronze", but later plan to cast Sterling as well.
Actually, the sand didn’t catch fire, the material used as a
binder (probably some oil based product) in it did. The
un-blackened portion of the sand is reuseable. If too much of the
binder has been driven out by heat or drying you’ll have a hard
time getting the sand to stick together after it’s rammed around
the model.
The blackened part is good for fill at your local land fill.
I delved into Sand Casting using Pro-Craft CASTING SAND. All
went well, however I was surprised at the Sand (or the binder
really) catching on fire. After breaking out I threw away the
burned parts but retained the unburned portion to reuse. That
remainder seemed ok and quite workable, is it?
Dear Edward, I do not know Pro-Craft Casting Sand, but I presume
that it is exactly like all the other castings sands used in
jewelry casting. Actually it is not sand but finely milled powder
of burned bricks, kept together with various sorts of oil. When
this oil is heated up by the molten metal, it evaporises, and it
is quite common that these vapours burst into flame in
connection with the oxygen in the air and the heat from the
metal, - normally not more than you can easily blow out with your
mouth. I throw away all the parts that have changed colour, and
also scrape off all the parts of the material which has come into
connection with talk or whatever one uses to separate the two
halves. I find the material so inexpensive that I don’t want to
take any risks here. Best regards from hot and sunny Denmark Niels
Loevschal
Ed, at one time or another I’ve tried greensand, oilsand, a 19th
century recipe for sand plus molasses, sand/clay and various
other concoctions. To date my favorite is a mixture of between 10
and 20% builder’s plaster in sand, mixed dry and then with enough
water added to make it adhere like greensand. It is packed just
like greensand (must be packed within 10 minutes of adding
water), with more air vents than I would need in greensand about
one every 1.5 inches and allowed to cure for an hour before
casting. The major disadvantage is that for objects with central
parting lines so the object extends above the cope/drag joint it
tends to not catch all the side spewing metal so there is a
flashing produced. But the molds, once set up can be take apart
and fiddled with, channels cut, detail modified et cetera with
much less worry than oilsand or greensand. It doesn’t stink like
oilsand, doesn’t steam as much as greensand, but it still needs
to be cast in a safe place on the ground so that side drips
don’t catch one’s shoes on fire.
No advice for you, just sharing the way I do it, casting
generally 2-4 pounds but up to 8 pounds on occasion. Sand casting
is not for beginners and I have the scars to prove it. 8-^)
I throw away all the parts that have changed colour, and
also scrape off all the parts of the material which has come into
connection with talk or whatever one uses to separate the two
halves. I find the material so inexpensive that I don't want to
take any risks here.
I thought this too. I recently taught a class using Delft clay
(the students all loved it by the way!) and after a few days of
this we were to my horror rapidly running out of sand. Then one
in the class (who shall remain un-named unless he joins the
discussion) revealed that he’s been using the blackened clay we’d
discarded. I guess it still had a useable amount of binder left
in it.
We wondered if the binder can be added back in or not. What do
people think?
The soot and ash would be hard to remove, so that’d remain, but
maybe with binder replenished the clay’d be recycled abd useable
as casting clay.
I am trying to track down an industrial source for the fine clay
Delft use. I think I’ve found a source called Petrobond. Yet to
compare it with Delft, which is remarkable fine and compacts
well.
Brian
B r i a n A d a m J e w e l l e r y E y e w e a r @Brian_Adam1 ph/fx +64 9 817 6816 NEW ZEALAND http://www.adam.co.nz/ New page up Wed 04th August 1999
I throw away all the parts that have changed colour, and
also scrape off all the parts of the material which has come into
connection with talk or whatever one uses to separate the two
halves I find the material so inexpensive that I don't want to
take any risks here
I thought this too I recently taught a class using Delft clay
(the students all loved it by the way!) and after a few days of
this we were to my horror rapidly running out of sand Then one
in the class (who shall remain un-named unless he joins the
discussion) revealed that he’s been using the blackened clay we’d
discarded I guess it still had a useable amount of binder left
in it
We wondered if the binder can be added back in or not What do
people think?
The soot and ash would be hard to remove, so that’d remain, but
maybe with binder replenished the clay’d be recycled abd useable
as casting clay
I am trying to track down an industrial source for the fine clay
Delft use I think I’ve found a source called Petrobond Yet to
compare it with Delft, which is remarkable fine and compacts
well
Brian
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I am he, who did a fantastically stimulating DELFT CASTING
workshop with Brian Adam last June, [ more about this later ] who
cannot abide waste at any expense, who tried to reuse the burned
out sand.
I found that with the whole class using the sand, and given that
we are by nature, wasteful when it comes to using the resources
of others, we tended to be over generous when scraping the burned
out sand from the mold so leaving a significant amount of still
good sand with that which was burned. Initially I tried to use it
as it was and found that the mold seemed to break down slightly
and give a rougher finish to the casting, so I then tried mixing
it well with clean sand [ 50, 50 ] and found that the results
were almost as good.
If anyone out there can tell us what the binding medium is, I
guess we would probably do somebody out of business, however,
when one is importing the stuff to this part of the world, one
doesn’t want to waste the resource, so I am continuing to
experiment with various oil based products 'till I strike a
suitable substitute binding medium.
Now about that course we did ! It was part of our Nelson
Polytechnic’s Winter Arts School, a five day program aimed at
like minded enthusiasts with a desire to learn from a group of
very talented craftspeople of whom Brian was one.
Brian’s workshop was aimed at passing on his knowledge and
skills of alloys and casting. We were a group of diversely
talented and experienced people who came away with a whole new
range of processes and enthusiasm to take our crafts and/or
professions to a new height. The whole course was well structured
around some very sound exercises based on the DELFT sand casting
process and traditional Japanese alloying processes which we
were able to adapt to our specific needs. Brian acted in the role
of tutor, mentor and facilitator. Thanks, Brian.
We have a small company here in Denmark who actually sell a
special oil to add to the casting sand if it has become too
dry. Haven’t tried it but I think any light engine oil would do.
The smoke from casting smells at least much like burning engine
oil. Best regards from Denmark, where the sun now is taking its
normal shape again.